*{
    margin: 0;
    padding: 0;
    font-family:"HanHei SC","PingHei","PingFang SC", "微软雅黑", 'Helvetica Neue', sans-serif;
}

ul{
    position: fixed;
    width: 100%;
    top:0;
    left: 0;
    z-index: 100;
    display: flex;
    flex-direction: row;
    justify-content: space-around;

    li{
        position:raletive;
        padding:8px;
        list-style: none;
        color: white;
        opacity: 0.7;
        transition: all 0.3s;
        cursor: pointer;

        &::before{
            content: '<';
            margin-left: -8px;
        }

        &::after{
            content: '>';
            margin-left: 0;
        }

        &::before,&::after{
            display: inline-block;
            position: absolute;
            opacity: 0;
            transition: all 0.3s;
        }

        &:hover::before{
            opacity: 1;
            margin-left:  -18px;
        }

        &:hover::after{
            opacity: 1;
            margin-left: 10px;
        }

        &:hover{
            opacity: 1;
        }
    }
}

